1. Technical Field
The technical field relates to a camera body that can be connected to an interchangeable lens, as well as to an imaging apparatus that includes an interchangeable lens and a camera body.
2. Related Art
JP-A-2006-215310 discloses an interchangeable lens system that includes a video camera (a camera body), an interchangeable lens for a single-lens reflex camera that can be connected to the camera body, and an intermediate adapter that connects the camera body and the interchangeable lens. Upon capturing subject images and sequentially generating image data, the camera body performs, using the intermediate adapter, AE (Auto Exposure) control on each of the sequentially generated image data by determining a driving amount and a driving speed of a diaphragm of the interchangeable lens. Specifically, the camera body sends a target video signal level and a detected video signal level to the intermediate adapter. The intermediate adapter determines a driving amount and a driving speed of the diaphragm of the interchangeable lens in accordance with a difference between the target video signal level and the detected video signal level, and sends, to the interchangeable lens, the driving amount and the driving speed thus determined respectively. The interchangeable lens controls the diaphragm at the driving amount and the driving speed thus received.
A conventional camera body is incapable of performing smooth AE control on each of image data generated by an imaging device for the following reasons. As exemplified in FIG. 8(a), it is assumed that a diaphragm value is set to “F8” at an interchangeable lens, that a sensitivity of a CMOS sensor is set to ISO “200” as well as an exposure time of the CMOS sensor is set to “ 1/30 second” for one frame at the camera body as imaging conditions for the CMOS sensor. In a case where a moving image is being captured under these conditions and the camera body sends, to the interchangeable lens, a control signal for regulating to “F4” information on a brightness of the interchangeable lens (such as the diaphragm value), the camera body performs, immediately after the control signal is sent, AE control under the imaging conditions (an ISO sensitivity “100” and an exposure time “ 1/60 second”) corresponding to the diaphragm value “F4” of the interchangeable lens. On the contrary, it takes some time for the diaphragm of the interchangeable lens to change from a state corresponding to the diaphragm value “F8” to a state corresponding to the diaphragm value “F4”, resulting in that there are several frames of images formed during the change in diaphragm value from “F8” to “F4”. Then, as shown in FIG. 8(b), during the change of the diaphragm, the camera body operates under the imaging conditions corresponding to the diaphragm value “F4” although the diaphragm of the interchangeable lens has not yet corresponded to the diaphragm value “F4”. Therefore, the camera body is incapable of performing the most appropriate AE control, and the CMOS sensor of the camera body outputs a moving image with unstable exposure. Such a moving image thus outputted may have an unstable brightness.
As described above, when there is a change in information on the brightness of the interchangeable lens (such as the diaphragm value), the conventional camera body has been incapable of performing appropriate AE control until completion of the change at the interchangeable lens correspondingly to the information on the brightness of the interchangeable lens. In other words, smooth AE control is not performed on each of the sequentially generated image data.